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Sterilizers
Sterilization 'Steam' An autoclave is a device to sterilize equipment and supplies by subjecting them to high pressure steam at 121° C or more. Sterilization (or sterilization, see spelling differences) refers to any process that effectively kills or eliminates transmissible agents (such as fungi, bacteria, viruses, spore forms, etc.) from a surface, equipment, article of food or medication, or biological culture medium. A widely-used method for heat sterilization is the autoclave, sometimes called a converter. Autoclaves commonly use steam heated to 121°C (250°F) or 134°C (270°F). To achieve sterility, a holding time of at least 15 minutes at 121°C or 3 minutes at 134°C is required. Additional sterilizing time is usually required for liquids and instruments packed in layers of cloth, as they may take longer to reach the required temperature (unnecessary in machines that grind the contents prior to sterilization). Following sterilization, liquids in a pressurized autoclave must be cooled slowly to avoid boiling over when the pressure is released. Modern converters operate around this problem by gradually depressing the sterilization chamber and allowing liquids to evaporate under a negative pressure, while cooling the contents. 'Phases' 1. Purge 2. Charge or Conditioning - vacuum and pressure pulses 3. Sterilize - 2 temps- 250°F or 270°F 4. Exhaust 5. Dry 'Cycles' 1. Gravity/Flash 2. Express (usually 2 pulses)/PreVac (usually 4 pulses) 3. Liquids 250°F or 121°C 'Ethylene Oxide' Ethylene oxide (EO or EtO) gas is commonly used to sterilize objects sensitive to temperatures greater than 60 °C such as plastics, optics and electrics. Ethylene oxide treatment is generally carried out between 30 °C and 60 °C with relative humidity above 30% and a gas concentration between 200 and 800 mg/L for at least three hours. Ethylene oxide penetrates well, moving through paper, cloth, and some plastic films and is highly effective. Ethylene oxide sterilizers are used to process sensitive instruments which cannot be adequately sterilized by other methods. EtO can kill all known viruses, bacteria and fungi, including bacterial spores and is satisfactory for most medical materials, even with repeated use. However it is highly flammable, and requires a longer time to sterilize than any heat treatment. The process also requires a period of post-sterilization aeration to remove toxic residues. Ethylene oxide is the most common sterilization method, used for over 70% of total sterilizations, and for 50% of all disposable medical devices. The two most important ethylene oxide sterilization methods are: (1) the gas chamber method and (2) the micro-dose method. To benefit from economies of scale, EtO has traditionally been delivered by flooding a large chamber with a combination of EtO and other gases used as dilutants (usually CFCs or carbon dioxide ). This method has drawbacks inherent to the use of large amounts of sterilant being released into a large space, including air contamination produced by CFCs and/or large amounts of EtO residuals, flammability and storage issues calling for special handling and storage, operator exposure risk and training costs Because of these problems a micro-dose sterilization method was developed in the late 1950s, using a specially designed bag to eliminate the need to flood a larger chamber with EtO. This method is also known as gas diffusion sterilization, or bag sterilization. This method minimizes the use of gas. 'Peracetic acid' Peracetic acid (also known as peroxyacetic acid, or PAA), is a organic compound with the formula CH3CO3H. This organic peroxide is a colorless liquid with a characteristic acrid odor reminiscent of acetic acid. It can be highly corrosive. Peracetic acid is a much weaker acid than the parent acetic acid, with a pKa of 8.2. Peracetic acid (0.2%) is used to sterilize instruments in the Steris system. 'Plasma' One of the more recent low-temperature plasma sterilizers is STERRAD® System by Advanced Sterilization Products, a Johnson & Johnson Company (Irvine, Calif). STERRAD® uses hydrogen peroxide vapor and low-temperature gas plasma to sterilize most devices quickly with no toxic residues. Usually, the process takes about 75 minutes for wrapped and dry instruments and devices. Inside the chamber, a deep vacuum is drawn. Fifty-nine percent (nominal) aqueous hydrogen peroxide is vaporized into the chamber. The product is then enveloped in the hydrogen peroxide vapor. Following the diffusion of the gaseous hydrogen peroxide through the load, chamber pressure is reduced, allowing for the generation of low-temperature gas plasma. Radio frequency (RF) energy is applied to the chamber via an RF amplifier, inducing the plasma state. Reactive species are generated from the hydrogen peroxide in this state, reacting with materials and each other. Once the high-energy species have reacted, they recombine to form water vapor, oxygen, and other non-toxic byproducts. Upon completion of sterilization, instruments are dry and wrapped/pouched for immediate use or sterile storage. Thus, re-contamination risk is minimized, and since they remain sterile until their next use, time and money is saved by avoiding reprocessing instruments if the case in canceled or delayed. The STERRAD® system takes up minimal space and requires no venting or water hookup. The only utility requirement is electrical hookup. Problem Solving Performance Checks *Door Seal *Smooth Door Movements *Date and Time *Jacket Pressure *Chamber Pressure *Steam Trap *Air Filter *Display *Printer Tests *Biological or spore *Daily Air Removal Test (DART) *Leak Test ** A vacuum is held to assure a leak tight chamber and no leaks within the piping system. An acceptable leak rate is any value less than 1mmHG read on the printed display. *Heat Indicator ** A heat sensitive tape similar to masking tape with cross stripes that detects the presence of extreme heat. Recall Normally, there are two reasons to recall loads that are bad and that's if the: 1. Biological test failed. 2. An opened pack in the OR and inside the instruments are still wet/ having condensate. References Links Category:CBET Study Info Category:Biomedical Engineering Technology